Many aqueous systems require thickeners in order to be useful for various types of applications. Such aqueous-based systems as cosmetics, protective coatings for paper and metal, printing inks, and latex paints all require the incorporation of thickeners in order to have the proper rheological characteristics for their particular uses. Many substances useful as thickeners are known in the art. These include natural polymers such as casein and alginates, and synthetic materials such as cellulose derivatives, acrylic polymers, and polyurethane polymers. Polyurethanes have found particular application as latex paint thickeners.
British Patent No. 1,069,735 teaches a process for making water soluble or water swellable surface active products. One aspect of G.B. 1,069,735 teaches that a polymer of the formula R--Y--A--Y--R wherein R is a hydrocarbon radical having more than 8 carbon atoms, Y is the group --NHCOO--, and A is a polyethylene glycol ether by reaction of a polyethylene glycol ether having a molecular weight of at least 1,000 with a monofunctional isocyanate of the formula RNCO wherein R is a hydrocarbon radical having more than 8 carbon atoms. Another aspect of G.B. 1,069,735 teaches that a polymer of the formula R--Y--(A--T).sub.n --A--Y--R wherein R is a hydrocarbon radical having more than 8 carbon atoms, Y is the group --NHCOO--, A is a polyethylene glycol ether, T is a diisocyanate residue, and n is a whole number .ltoreq.10 can be made by reaction of a polyethylene glycol ether having a molecular weight of at least 1,000 with a monofunctional isocyanate of the formula RNCO wherein R is a hydrocarbon radical having more than 8 carbon atoms. A third aspect taught by G.B. 1,069,735 is that a polymer of the formula R--X--(A--T).sub.n --A--X--R wherein R is a hydrocarbon radical having more than 8 carbon atoms; x is the group --NHCOO--, --SCONH--, --NHCONH--, N--CONH--, or --CONH--; A is a polyethylene glycol ether, T is the diisocyanate residue, and n is a whole number .ltoreq.10 by reaction of a polyethylene glycol ether having a molecular weight of at least 1,000 and a diisocyanate so that an excess of isocyanate groups is present over those needed to react with the hydroxyl groups of the polyethylene glycol and a monofunctional alcohol, mercaptan, phenol, or carboxylic acid or a primary or secondary amine, said monofunctional compound has a hydrocarbon radical having more than 8 carbon atoms; in which process the total amount of hydrocarbon radical which contains more than 8 carbon atoms does not amount to &gt;6% by weight of the reaction product. Japanese Kokai Patent 48-97783 teaches that compounds of the formula ##STR1## wherein Z is a polyether polyol residue derived from a compound containing active hydrogen atoms and alkylene oxide in which the polyether contains 20%-90% by weight oxyethylene groups; m is a number ranging from 2 to 8 and which signifies the number of hydroxyl groups per polyether polyol molecule; A is the residue of a divalent organic group such as a tolylene diisocyanate residue; Y is a residue of a compound containing active hydrogen atoms such as an ethoxylated C.sub.14 aliphatic alcohol; and n is a number equal to at least 3, can be used as thickeners in aqueous media such as in latex paints. U.S. Pat. No. 4,079,028 teaches a latex paint composition containing an emulsion polymer and from 0.1 to about 10% by weight based on emulsion polymer solids of a thickener selected from polymers of Groups A, B, and C. Polymers of group A are linear polymers of the formula A--B.sub.p --E.sub.q --(B--E).sub.m --B.sub.r --E.sub.t --A wherein each of p, q, r, and t independently is zero or 1; at least one of q and r is 1, and t is zero when r is zero; provided that, when q is 1, then: (a) each of p, r, and t is zero; or (b) p is zero and each of r and t is 1; or (c) t is zero and each of r and p is 1; and when q is zero, then r is 1 and each of p and t is zero; A is a hydrophobic organic radical containing at least one carbon atom; B is a divalent hydrophobic group of the structure ##STR2## where G is the residue of an organic di- or tri-isocyanate; E is a divalent, hydrophilic, nonionic polyether groups of molecular weight of at least about 1,500 and m is at least 1. Polymers of group B are designated as star-shaped products of the formula [H--E--OCH.sub.2 ].sub.s L[Q.sub.v --(D.sub.u --E--A).sub.w R.sub.z ].sub.m where L is X, Y or --O--, Q is --CH.sub.2 C.tbd., D is --CH.sub.2 O--, m is 2-4, s is zero to 2, the sum of m and s is the valence of L, w is 1-3, and each of u and z independently is zero or 1; and where X is a hydrocarbon radical containing at least 1 carbon atom, preferably 1-4 carbon atoms; and Y is a trivalent radical selected from --OCONH(CH.sub.2).sub.6 N[CONH(CH.sub.2).sub.6 NHCO--O].sub.2 --, CH.sub.3 C[CH.sub.2 --O--OCNHC.sub.7 H.sub.6 NHCO].sub.3 --, and CH.sub.3 CH.sub.2 C[CH.sub.2 --O--OCNHC.sub.7 H.sub.6 NHCO].sub.3 -- provided that: (a) when L is X, then u and w are each 1, v and z are each zero, the sum of m and s is 4, and m is at least 2; (b) when L is Y, then u, v and s are each zero, m is 3, w is 2-3, and z is zero or 1; (c) when L is --O--, then v and u are each 1, m is 2, w is 1-3, and each of s and z is zero. Polymers of group c are complex mixtures of linear, branched, and sub-branched products which form networks or hydrophobes and hydrophobic segments interspersed with hydrophilic segments. The essential elements of these polymers are a polyfunctional compound containing at least 3 hydroxyl or isocyanate groups, a di-functional compound reactive with the polyfunctional compound, and a monofunctional reactant such as a monohydroxy or monoamino compound. U.S. Pat. No. 4,155,892 teaches a composition consisting essentially of water and an amount of a thickener polymer selected from the polymers disclosed in U.S. Pat. No. 4,079,028 above to thicken the water. U.S. Pat. No. 4,499,233 teaches a water dispersible modified polyurethane which is the product of the reaction of: (a) a polyisocyanate; (b) a polyether polyol; (c) a modifying agent which is a multifunctional compound such as .alpha.,.omega.-amino alkanes and aromatic diamines such as 1,4-diaminobenzene; and (d) a capping agent such as a monoisocyanate. U.S. Pat. No. 4,499,233 also teaches a thickened aqueous composition comprised of water and from about 0.005 to about 10.00% by weight of a water dispersible modified polyurethane as disclosed above.
U.S. Pat. No. 4,426,485 teaches thickeners for aqueous systems which are water-soluble polymers having a molecular weight of at least 10,000 and which are comprised of hydrophobic segments each containing at least one monovalent hydrophobic group covalently bonded to the polymer. At least one of the hydrophobic segments has at least two hydrophobes thereby forming a bunch of hydrophobes within the hydrophobic segment. The hydrophobes within a bunched hydrophobic segment are in close association when they are separated by no more than about 50 covalently bonded, sequentially connected atoms. One example of such a polymer is made by reacting a polyurethane pre-polymer comprised of PEG 8000 and toluene diisocyanate with toluene diisocyanate and the diol formed by reaction of epichlorohydrin and a 10 mole ethylene oxide adduct of nonyl phenol.
A non-urethane thickener is disclosed in U.S. Pat. No. 3,770,684 which teaches latex compositions containing from about 0.1% to about 3.0% of a compound of the general formula R--X--(water soluble polyether)--X--R' wherein R and R' are water insoluble hydrocarbon residues; X is a connecting linkage selected from the group consisting of an ether linkage, an ester linkage, an amide linkage, an imino linkage, a urethane linkage, an sulfide linkage, or a siloxane linkage. U.S. Pat. No. 3,770,684 also teaches that the preferred water soluble polyether is a polyethylene oxide polymer having a molecular weight of from 3,000 to 35,000 or an ethylene oxide-propylene oxide copolymer having a molecular weight of from 3,000 to 35,000.